perf: stop per-frame SQLite writes and console spam, make perf.log opt-in

- Explorer: the tip check runs every frame the Explorer tab is open,
  and it read both tip rows and rewrote them each time (two autocommit
  WAL writes per frame). A steady tip is now kept in memory and skips
  SQLite. A new tip writes both rows in one savepoint, so a crash
  between them can't pair a new height with the old hash. A test
  checks that 100 steady checks write nothing.
- Console: while the daemon was in the Error state the Console tab
  added its error line on every poll, i.e. every frame, re-laying out
  the whole buffer each time. It prints once per error now: on entering
  Error, when the message changes, or after another crash
  (EmbeddedDaemon::getUnexpectedExitCount(), never reset). setState
  writes the message before the state, so a reader that sees Error sees
  that error's message. The stray " ===" suffix is gone.
- perf.log: the profiler appended a block every 300 frames on every
  run and never rotated the file (tens of MB a day for a wallet left
  open). It is now off unless the app starts with DRAGONX_PERFLOG=1;
  otherwise its zone hooks are near no-ops.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/daemon/embedded_daemon.cpp

@@ -256,11 +256,13 @@ std::vector<std::string> EmbeddedDaemon::getChainParams()
 
 void EmbeddedDaemon::setState(State s, const std::string& message)
 {
-    state_ = s;
+    // Message first, state second: a reader that sees Error must also see that error's message, not the
+    // previous one (the console prints the message when it sees the state change).
     if (!message.empty() && s == State::Error) {
         std::lock_guard<std::mutex> lk(error_mutex_);   // dedicated mutex — never taken with output_mutex_ held
         last_error_ = message;
     }
+    state_ = s;
 
     if (state_callback_) {
         state_callback_(s, message);
@@ -1098,6 +1100,7 @@ void EmbeddedDaemon::monitorProcess()
         }
         
         crash_count_++;
+        unexpected_exits_++;   // before setState(Error): a reader that sees Error sees the new count
 
         // Build informative error message with full diagnostic details
         std::string error_msg = "dragonxd exited unexpectedly (" + translateWindowsExitCode(exit_code) + ")";
@@ -1671,6 +1674,7 @@ void EmbeddedDaemon::monitorProcess()
                     return;
                 }
                 crash_count_++;
+                unexpected_exits_++;   // before setState(Error): a reader that sees Error sees the new count
                 setState(State::Error, "dragonxd exited unexpectedly (" + exitInfo + ")");
                 return;
             }